Obesity is a major health concern in Western societies. It is estimated that about 146 million adults in the United States are overweight or obese. Epidemiological studies have shown that increasing degrees of overweight and obesity are important predictors of decreased life expectancy. Obesity causes or exacerbates many health problems, both independently and in association with other diseases. The medical problems associated with obesity, which can be serious and life-threatening, include hypertension; type 2 diabetes mellitus; elevated plasma insulin concentrations; insulin resistance; hyperinsulinemia; glucose intolerance; dyslipidemias; hyperlipidemia; endometrial, breast, prostate and colon cancer; osteoarthritis; respiratory complications, such as obstructive sleep apnea; cholecystitis; cholelithiasis; gout; gall bladder disease; respiratory problems; psychological disorders (such as depression, eating disorders, distorted body image and low self esteem); arteriosclerosis; heart disease; abnormal heart rhythms; angina pectoris; and heart arrythmias (Kopelman, P. G., Nature 404, 635-643 (2000)). Obesity is further associated with premature death and with a significant increase in mortality and morbidity from stroke, myocardial infarction, congestive heart failure, coronary heart disease, and sudden death. Recent studies have found that obesity and its associated health risks also affect children and adolescents.
Obesity is now recognized as a chronic disease that requires treatment to reduce its associated health risks. Important outcomes for the treatment of obesity include weight loss, and weight management to improve cardiovascular and metabolic health and to reduce obesity-related morbidity and mortality. It has been shown that 5-10% loss of body weight can substantially improve metabolic values, such as blood glucose, blood pressure, and lipid concentrations. Hence, it is believed that a 5-10% intentional reduction in body weight may reduce morbidity and mortality.
Rodent genetics and pharmacology have implicated Bombesin receptor subtype-3 (BRS-3) in the development of obesity and diabetes (Ohki et al. Nature 390: 165-69 (1997)). BRS-3 is a G protein coupled receptor expressed primarily in the central nervous system, particularly the hypothalamus, a major region in the central nervous system for the regulation of food intake, metabolic rate, and body weight (Liu et al. Biochem 41: 8154-8160 (2002)). Bombesin, bombesin-like peptides, and related receptors participate in a diverse array of physiological processes. Although the natural ligand for the BRS-3 receptor has not yet been identified, bombesin-like peptides are widely distributed in the central nervous system and the gastrointestinal tract, where they bind to bombesin receptor subtype-3 (BRS-3), neuromedin B, and gastrin-releasing peptide (GRP-R) receptors, and modulate smooth muscle contraction, exocrine and endocrine processes, metabolism and behavior. BRS-3 has been implicated in the regulation of neuroendocrine function and energy metabolism (Ohki et al. Nature 390: 165-69 (1997)). One study showed that mice lacking the bombesin subtype-3 (BRS-3) receptor develop metabolic defects and obesity (Ohki et al. Nature 390: 165-69 (1997)). Specifically, mice lacking functional BRS-3 are hyperphagic and have a reduced metabolic rate, reduced core temperature which leads to the development of obesity, insulin resistance, diabetes and hypertension as they age. Additionally, bombesin-like peptides may contribute to the pathogenesis of some human carcinomas (For review' see Lebacq-Verheyden et ale in Handbook of Experime'tal Pharmacology, Sporn, M. N. and Roberts, A. B., eds., Vol. 95, pp. 71-124, Springer-Nierlag, Berlin). There is also evidence of a role for BRS-3 in cell growth and wound repair (Tan et al. Peptides 27:1852-58 (2006)) and its distribution in the rat gastrointestinal tract suggests a role in regulation of gut motility (Porcher et al., Cell Tissue Res 320:21-31 (2005).
BRS-3 agonists to treat obesity/diabetes are disclosed in WO 2005/080390, WO 2005/056532, and WO 2003/104196. Imidazole compounds useful for the treatment of obesity and/or diabetes have been disclosed in WO 04/058176, WO 04/071447, WO 04/048351, WO 04/046091, WO 05/035551, US 2005/0187277 and US 2005/0272778. Other imidazoles are disclosed in WO 93/17681, WO 98/28269, WO 99/32454, WO 04/007464, and JP 7-243068.
Weight loss drugs that are currently used in monotherapy for the treatment of obesity have limited efficacy and significant side effects. Because of the unresolved deficiencies of the various pharmacological agents used in the treatment of obesity and diabetes, there is a continuing need for a weight loss treatment with enhanced efficacy and fewer undesirable side effects. The instant invention addresses this problem by providing bombesin receptor agonists, and in particular selective agonists of the bombesin receptor subtype-3 (BRS-3), useful in the treatment and prevention of obesity, diabetes, obesity-related disorders, and diabetes related disorders.